Computation of Net Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Computation of Net Earnings per Share
Net income available to common stockholders	$ 13,932	$ 2,937	$ 23,438	$ 4,885
Weighted average common shares outstanding used in computing basic income per share	30,589	29,097	30,183	29,066
Incremental options and RSUs	2,579	1,604	2,596	1,541
Weighted average common shares outstanding used in computing diluted net income per share	33,168	30,701	32,779	30,607
Net income per share
Basic	$ 0.46	$ 0.10	$ 0.78	$ 0.17
Diluted	$ 0.42	$ 0.10	$ 0.72	$ 0.16
Weighted average number diluted shares outstanding adjustment	6	900	300	900